In the past, the design and development of total knee replacement prostheses for diseased and/or damaged human knees have typically been restricted to no more than three factory-assembled components; namely, the femoral, tibial and patellar replacement components. These devices have been designed to fit the anatomical variations and surgical needs of the largest possible segment of the eligible population while maintaining a manageable inventory of component parts. Such prior art designs typically incorporate plastic tibial articulating surfaces which are permanently assembled at a factory to a metal base plate having some configuration of a rigid, integral stem which extends down into the tibial plateau surface.
Due to the wide variations of natural, anatomical configurations of the human proximal tibia, the unpredictable bone quality of the tibial plateau and the varying degrees of deterioration resulting from arthritis, trauma, or failed previous prostheses, a need has existed for a versatile tibial prosthesis which can be custom fit to meet the needs presented by the above-described variables.
Also, because joint prostheses in general, and particularly knee replacements, are being implanted in patients with increasingly longer life expectancies, the need also exists for a prosthesis which allows for later replacement of a worn bearing surface without disturbing the components firmly affixed in or to the bones.
It is therefore an object of the present invention to provide an implantable knee joint prosthesis which allows several of its component parts to be mass produced while allowing a custom fit for each patient and his or her particular therapeutic need. It is also an object of the present invention to allow such custom fitting to be easily accomplished without sacrificing overall prosthesis quality and performance. This feature also provides the surgeon with a selection of a number of articulating/bearing surfaces with varying amounts of constraint, and congruency with the femoral component for patients with various degrees of soft tissues laxity which could not be preoperatively anticipated. The surgeon may therefore tailor the implant to better fit the patient's knee as it is found to exist and thereby decrease the probability that the knee prosthesis would require future adjustment, modification or replacement.
Finally, it is an object of the invention to provide a knee prosthesis which allows for later replacement of worn bearing surfaces without the necessity of disturbing and/or replacing those components of the prosthesis which have been and remain firmly affixed to their respective bones.
These and other advantages will become apparent to one of ordinary skill in the art in light of the following disclosure, drawings and claims.